1. Field of the Disclosure
The present disclosure relates to electronic devices, more particularly, to electronic devices that include discontinuous storage elements and process for forming them.
2. Description of the Related Art
A process of forming a nonvolatile memory cell within an electronic device can include forming a charge storage stack. The charge storage stack can be formed by depositing discontinuous storage elements (“DSEs”) over a thermally grown oxide layer and then forming another dielectric layer over the DSEs to substantially encapsulate the DSEs. Forming a film over of the DSEs is problematic. The film can be formed by thermally growing it from the material within the DSEs; however, this process consumes the DSEs radially. Thus, as the encapsulation layer increases in thickness, the radius of the individual DSEs is reduced by a value linearly, but the volume of an individual DSE is reduce by a cubic function of the same value. Also, the DSEs may not include a material that forms an insulating oxide or nitride. Alternatively, the film can be deposited using (i) silane (SiH4) or dichlorosilane (SiCl2H2) and (ii) an oxygen-containing gas or a nitrogen-containing gas.
The nonvolatile memory cell can be programmed by hot carrier injection (“HCI”). When the overlying film includes the deposited film, electron traps can be formed within the deposited film. The presence of such electron traps degrades the dielectric properties of the dielectric material such that eventually, the charge storage region is no longer electrically floating and is unable to store charge. A thermally grown film is less likely to form traps; however, the DSEs are consumed during formation of the thermally grown film.
Skilled artisans appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of embodiments of the invention. The use of the same reference symbols in different drawings indicates similar or identical items.